During the lifetime of a patient, it may be necessary to perform a joint replacement procedure or anthroplasty on the patient as a result of, for example, disease or trauma. One such type of joint replacement procedure is a hip replacement procedure in which a diseased and/or damaged hip joint is replaced with a prosthetic hip joint. A typical hip replacement procedure utilizes a prosthesis that generally includes a femoral stem component, a proximal body component, and a neck segment. The femoral stem is implanted in a prepared medullary canal of the patient's femur.
During performance of such a hip replacement procedure, the surgeon must evaluate the size and condition of the patient's bones (e.g. the patient's femur) in order to determine the proper type and configuration of each of the various types of prosthetic components that are to be implanted. One or more provisional components are temporarily fixed to a bone prior to permanent fixation of the prosthetic joint. The provisional components are intended to mimic certain aspects of the permanent prosthetic joint in order for a surgeon to validate measurements and to test several different possible component sizes and shapes. Hence, provisional components are aptly known as “trials”, and the procedure is known as “trialing.”
Currently, in a majority of revision total hip arthroplasties, the bone has little or no supportive metaphysis or diaphyseal areas. This makes it difficult for surgeons to reproduce the proper anatomy. To do this, the surgeon may use a distally fixed implant. This facilitates trialing from the distal femoral cortex and subsequent proximal anatomy. Many trials are used in surgery having one basic anterior/posterior proximal anatomical body with altering characteristics (i.e., stem lengths, bow, offsets, neck lengths, neck anteversion). Each instance requires a single monolithic trial that duplicates the implant, which is therein made from casting substrate.
Other modular devices contain modular similarities but may not address multi-functional characteristics as per using both neck segments and distal stem variations simultaneously. They also may not use pre-existing broach system neck segments and its instrumentation technology to simplify case sizing.
Other techniques require that the broach be removed from the medullary canal to allow the use of a trial having a stem portion, a head and a neck. For example, U.S. Pat. No. 5,100,407 discloses a system including a group of variously sized trial neck/body portions and a group of differing length trial stem portions which are mixed and matched to create a suitable trial. However, repetitive removal and insertion of successions of trial stems accompanied by successive assembly and disassembly with respect to the body can require more time, which will increase operating room cost.
Another known trial includes a stem to which a collar is secured at successive points along the length of the trial until an appropriate neck length and stem length have been ascertained. Undesirably, this type of trial induces measurement inaccuracies resulting from stem movement as the collar is repeatedly engaged and disengaged from the stem. Additionally, as the collar is moved toward the distal end of the stem, less of the stem is disposed within the medullary canal, causing the trial to become increasingly unstable and rendering accurate measurements difficult to achieve.
Any additional anatomical complexity can increase the undesirable numbers of trial components in a kit. For example, trials for long hip stems must be different for the right and left femur due to the curvature or bow of the respective femurs. In other words, a long left stem trial cannot be used in the right femur and vice versa. It is believed that a trial system consisting of numerous parts that must be selected and mated in various combinations, possibly many times, is cumbersome.
Another example, U.S. Pat. No. 6,193,759, uses two component embodiments but has not included an additional neck segment component that encompasses different geometries. The '759 patent does not address the ability to be used on one single broaching system. The system of the '759 patent also does not used the same instrument system to implant or extract both the broach and trial.
Because many variations in sizes and shapes of trials are required to be available to the surgeon, it is necessary to maintain a large inventory of trials and/or trial components. Such a large inventory is costly, occupies valuable operating room space, and is difficult to manage. Another problem is that if a trial is to be assembled from multiple components, the assembly and disassembly of the trial can consume large periods of operating room time.
What is needed therefore is a femur implant trial that can be quickly and easily assembled and disassembled from multiple components.
What is further needed therefore is an apparatus and method for assembling various sizes and shapes of trials from a minimum number of components to be kept in inventory.